A digital image is a collection of pixels, typically arranged in an array, which defines an optically formed reproduction of one or more objects, backgrounds or other features of a scene. In a digital image, each of the pixels represents or identifies a color or other light condition associated with a portion of such objects, backgrounds or features. For example, a black-and-white digital image includes a single bit for representing a light condition of the pixel in a binary fashion (e.g., either black or white), while a grayscale digital image may represent the light condition in multiple bits (e.g., two to eight bits for defining tones of gray in terms of percentages or shares of black-and-white), and a color digital image may include groups of bits corresponding to each of a plurality of base colors (e.g., red, green or blue), and the groups of bits may collectively represent a color associated with the pixel. One common digital image is a twenty-four bit (24-bit) color digital image, in which each of the pixels includes three channels of eight bits each, including a first channel of eight bits for describing an extent of red within a pixel, a second channel of eight bits for describing an extent of green within the pixel, and a third channel of eight bits for describing an extent of blue within the pixel.
A depth image, or depth map is also a collection of pixels that defines an optically formed reproduction of one or more objects, backgrounds or other features of a scene. Unlike the pixels of a digital image, however, each of the pixels of a depth image represents or identifies not a light condition or color of such objects, backgrounds or features, but a distance to objects, backgrounds or features. For example, a pixel of a depth image may represent a distance between a sensor of an imaging device that captured the depth image (e.g., a depth camera or range sensor) and the respective object, background or feature to which the pixel corresponds.
A depth image or depth map can be determined by comparing two or more digital images that are obtained by cameras that are separated by a known baseline to determine a disparity between correlated pixels of the two or more digital images. The accuracy of the computed depth information of a depth map is often dependent on the accuracy of the baseline and the alignment or calibration of the two or more imaging elements. During operation of an aerial vehicle, such as an unmanned aerial vehicle (UAV), determining depth information, or distances between an object represented in images and the aerial vehicle is often important to ensure that the aerial vehicle can avoid those objects.
While implementations are described herein by way of example, those skilled in the art will recognize that the implementations are not limited to the examples or drawings described. It should be understood that the drawings and detailed description thereto are not intended to limit implementations to the particular form disclosed but, on the contrary, the intention is to cover all modifications, equivalents and alternatives falling within the spirit and scope as defined by the appended claims. The headings used herein are for organizational purposes only and are not meant to be used to limit the scope of the description or the claims. As used throughout this application, the word “may” is used in a permissive sense (i.e., meaning having the potential to), rather than the mandatory sense (i.e., meaning must). Similarly, the words “include,” “including,” and “includes” mean “including, but not limited to.” Additionally, as used herein, the term “coupled” may refer to two or more components connected together, whether that connection is permanent (e.g., welded) or temporary (e.g., bolted), direct or indirect (i.e., through an intermediary), mechanical, chemical, optical, or electrical. Furthermore, as used herein, “horizontal” flight refers to flight traveling in a direction substantially parallel to the ground (i.e., sea level), and that “vertical” flight refers to flight traveling substantially radially outward from the earth's center. It should be understood by those having ordinary skill that trajectories may include components of both “horizontal” and “vertical” flight vectors.